@inproceedings{HartmannKnoppLenskietal., author = {Hartmann, J{\"u}rgen and Knopp, Kevin and Lenski, Philipp and Z{\"a}nglein, Marc and Manara, Jochen and Stark, Thomas and Zipf, Matthias and Arduini, Mariacarla and Schreiber, Ekkehard and Kr{\"u}ger, U. and Schmidt, Franz and Brunner, Martin}, title = {Sensor systems for additive manufacturing}, publisher = {Key Note Lecture MSE 2018}, address = {Darmstadt}, language = {en} } @incollection{HartmannReichling, author = {Hartmann, J{\"u}rgen and Reichling, M.}, title = {Thermal characterization of diamond materials}, series = {Properties and growth of diamond}, booktitle = {Properties and growth of diamond}, editor = {Nazar{\´e}, H. and Neves, A.J.}, publisher = {Institution of Electrical Engineers}, address = {London}, language = {en} } @inproceedings{HartmannAnhaltHollandtetal., author = {Hartmann, J{\"u}rgen and Anhalt, Klaus and Hollandt, J{\"o}rg and Taubert, Dieter Richard and Werner, L.}, title = {Optische Hochtemperaturmesstechnik f{\"u}r die Thermometrie, Radiometrie und Photometrie}, address = {N{\"u}rnberg}, language = {en} } @inproceedings{HartmannOchsLenskietal., author = {Hartmann, J{\"u}rgen and Ochs, Dennis and Lenski, Philipp and Schiffler, Andreas and Versch, Alexander and Manara, Jochen}, title = {Thermal process monitoring for additive manufacturing}, address = {Darmstadt}, language = {en} } @inproceedings{HartmannLenskiOchsetal., author = {Hartmann, J{\"u}rgen and Lenski, Philipp and Ochs, Dennis and Shandy, Amir and Winterstein, A. and Versch, Alexander and Schiffler, Andreas}, title = {Thermische Prozess{\"u}berwachung f{\"u}r additive Fertigungsverfahren}, address = {Berlin}, language = {de} } @article{KnoppShandyManaraetal., author = {Knopp, Kevin and Shandy, Amir and Manara, Jochen and Vidi, Stephan and Hartmann, J{\"u}rgen}, title = {Metrologische Apparaturen zur Messung thermophysikalischer Materialeigenschaften bei sehr hohen Temperaturen im EU-Projekt Hi-TRACE}, series = {FHWS Science Journal}, volume = {5}, journal = {FHWS Science Journal}, number = {2}, issn = {2196-6095}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:863-opus-20046}, pages = {83 -- 92}, abstract = {Industriezweige wie die Glas-Industrie, die Kraftwerkstechnik sowie die Luft- und Raumfahrttechnik m{\"u}ssen kontinuierlich neue Methoden entwickeln, sowie bestehende Verfahren optimieren, um in ihren Bereichen wettbewerbsf{\"a}hig zu sein bzw. neue Anforderungen an Umwelt- und Klimaschutz zu erf{\"u}llen. Dies beinhaltet oft die Entwicklung neuer Materialien, die leichter zu fabrizieren sind und sowohl mechanisch als auch thermisch h{\"o}heren Belastungen standhalten. F{\"u}r die genannten Industriezweige sind Prozesse mit hohen Betriebstemperaturen bis zu 3.000 °C kennzeichnend und damit ist die Kenntnis von Materialeigenschaften bei diesen extremen Temperaturen von großer Bedeutung. Auch wenn es bereits einige Messapparaturen f{\"u}r die Bestimmung von thermophysikalischen Materialdaten bei hohen Temperaturen gibt, muss die R{\"u}ckf{\"u}hrung dieser auf die SI Basiseinheiten gew{\"a}hrleistet werden, um die Zuverl{\"a}ssigkeit der gemessenen Daten f{\"u}r die Anforderung der genannten Branchen sicherzustellen. Diese Aufgabe ist das Ziel des EMPIR-(European Metrology Programme for Innovation and Research) Projektes Hi-TRACE [1]. Hi-TRACE zielt darauf ab, Referenzapparaturen und neue Methoden f{\"u}r die Messung von thermophysikalischen Materialeigenschaften, (thermische Diffusivit{\"a}t, spezifische W{\"a}rme, Emissionsgrad und Schmelztemperatur) sowie der Haftung von Schichten {\"u}ber 1.000 °C zu bestimmen.}, language = {de} } @article{OchsWehnertKnoppetal., author = {Ochs, Dennis and Wehnert, Kira-Kristin and Knopp, Kevin and Hartmann, J{\"u}rgen and Versch, Alexander and Schiffler, Andreas}, title = {Untersuchungen zur Temperaturleitf{\"a}higkeit additiv gefertigter Stahlproben in Abh{\"a}ngigkeit der relativen Dichte}, series = {FHWS Science Journal}, volume = {5}, journal = {FHWS Science Journal}, number = {2}, issn = {2196-6095}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:863-opus-19986}, pages = {75 -- 82}, abstract = {Das direkte Metall-Laser-Schmelzen (DMLS) aus der Familie der Additiven Fertigungsverfahren (AM) erm{\"o}glicht die schichtweise Erzeugung komplexer dreidimensionaler Geometrien mit hoher relativer Dichte unter Verwendung von Metallpulver als Ausgangsmaterial [1]. Die Technologie wird zunehmend eingesetzt, um innovative Bauteile material- und gewichtssparend herzustellen oder komplexe Produkte ohne zus{\"a}tzliche Werkzeuge oder Spannvorrichtungen zu fertigen. Dar{\"u}ber hinaus sind Funktionsintegrationen, zum Beispiel Gussformen mit eingepr{\"a}gten K{\"u}hlkan{\"a}len, m{\"o}glich. Da einzelne Metallpulverschichten auf vorhergehende Schichten aufgeschmolzen werden, entstehen w{\"a}hrend der Herstellung des Bauteils komplexe, zeitabh{\"a}ngige Temperaturprofile [2]. Durch den Einsatz hoher Laserintensit{\"a}ten und Scangeschwindigkeiten, bei denen die Belichtungszeit der Laserbestrahlung im Bereich von Millisekunden liegt, werden zudem extrem hohe Aufheiz- und Abk{\"u}hlraten induziert, die zu einzigartigen Mikrostrukturen und Materialeigenschaften f{\"u}hren [3]. Diese extremen Prozessbedingungen k{\"o}nnen sich jedoch auch negativ auf den Fertigungsprozess auswirken. Bei komplexen Bauteilen bleibt die Prozessstabilit{\"a}t und Qualit{\"a}tssicherung Umfragen zufolge weiterhin die wichtigste technologische Barriere f{\"u}r den Einsatz additiv gefertigter Bauteile in hochbelasteten oder sicherheitsrelevanten Bereichen [4]. Daher verspricht der Zusammenhang zwischen Temperaturprofil w{\"a}hrend der Fertigung, relativer Dichte der Bauteile, sowie thermophysikalischer Eigenschaften additiv gefertigter Proben wichtige Erkenntnisse, insbesondere im Hinblick auf eine zerst{\"o}rungsfreie Qualit{\"a}tssicherung, sowie neue Anwendungsm{\"o}glichkeiten.}, language = {de} } @article{JuergenArduiniManaraetal., author = {J{\"u}rgen, Hartmann and Arduini, Mariacarla and Manara, Jochen and Stark, Thomas and Ebert, Hans-Peter}, title = {Development and Evaluation of an Improved Apparatus for Measuring the Emissivity at High Temperatures}, series = {Sensors}, volume = {21}, journal = {Sensors}, number = {18}, issn = {1424-8220}, doi = {10.3390/s21186252}, abstract = {An improved apparatus for measuring the spectral directional emissivity in the wavelength range between 1 µm and 20 µm at temperatures up to 2400 K is presented in this paper. As a heating unit an inductor is used to warm up the specimen, as well as the blackbody reference to the specified temperatures. The heating unit is placed in a double-walled vacuum vessel. A defined temperature, as well as a homogenous temperature distribution of the whole surrounding is ensured by a heat transfer fluid flowing through the gap of the double-walled vessel. Additionally, the surrounding is coated with a high-emitting paint and serves as blackbody-like surrounding to ensure defined boundary conditions. For measuring the spectral directional emissivity at different emission angles, a movable mirror is installed in front of the specimen, which can be adjusted by a rotatable arrangement guiding the emitted radiation into the attached FTIR-spectrometer. The setup of the emissivity measurement apparatus (EMMA) and the measurement procedure are introduced, and the derived measurement results are presented. For evaluating the apparatus, measurements were performed on different materials. The determined emissivities agree well with values published in literature within the derived relative uncertainties below 4\% for most wavelengths.}, language = {en} } @article{WehnertOchsSchmittetal., author = {Wehnert, Kira-Kristin and Ochs, Dennis and Schmitt, Jan and Hartmann, J{\"u}rgen and Schiffler, Andreas}, title = {Reducing Lifecycle Costs due to Profile Scanning of the Powder Bed in Metal Printing}, series = {Procedia CIRP 98}, volume = {98}, journal = {Procedia CIRP 98}, publisher = {Elsevir}, pages = {684 -- 689}, abstract = {First time right is one major goal in powder based 3D metal printing. Reaching this goal is driven by reducing life cycle costs for quality measures, to minimize scrap rate and to increase productivity under optimal resource efficiency. Therefore, monitoring the state of the powder bed for each printed layer is state of the art in selective laser melting. In the most modern approaches the quality monitoring is done by computer vision systems working with an interference on trained neural networks with images taken after exposure and after recoating. There are two drawbacks of this monitoring method: First, the sensor signals - the image of the powder bed - give no direct height information. Second, the application of this method needs to be trained and labeled with reference images for several cases. The novel approach presented in this paper uses a laser line scanner attached to the recoating machine. With this new concept, a direct threshold measure can be applied during the recoating process to detect deviations in height level without prior knowledge. The evaluation can be done online during recoating and feedback to the controller to monitor each individual layer. Hence, in case of deviations the location in the printing plane is an inherent measurement and will be used to decide which severity of error is reported. The signal is used to control the process, either by starting the recoating process again or stopping the printing process. With this approach, the sources of error for each layer can be evaluated with deep information to evaluate the cause of the error. This allows a reduction of failure in the future, which saves material costs, reduces running time of the machine life cycle phase in serial production and results in less rework for manufactured parts. Also a shorter throughput time per print job results, which means that the employee can spent more time to other print jobs and making efficient use of the employee's work force. In summary, this novel approach will not only reduce material costs but also operating costs and thus optimize the entire life cycle cost structure. The paper presents a first feasibility and application of the described approach for test workpieces in comparison to conventional monitoring systems on an EOS M290 machine.}, language = {en} } @article{GielingerBohnDeinzeretal., author = {Gielinger, Sebastian and Bohn, Gunther and Deinzer, Frank and Linke, Andreas}, title = {Investigation of an inline inspection method for the examination of cylinder-like specular surfaces using deflectometry}, series = {applied sciences}, volume = {12}, journal = {applied sciences}, number = {13}, issn = {2076-3417}, abstract = {An optical measuring method is presented, with which it is possible to measure and evaluate reflective cylindrical surfaces using a combination of deflectometry and subsequent reconstruction of the surface. The system is set up and tested on rolling elements of cylindrical roller bearings. However, it is not limited to this use case and can be applied to other cylindrical specular surfaces. The system distinguishes itself from existing test methods through the combination of high-resolution three-dimensional defect measurement with a very short recording time, and offers the possibility of introducing tolerance limits in the production of cylindrical specular surfaces. With this method, it is possible to record a defect with the dimensions of 1.3 mm by 1.8 mm within 5 s and to reconstruct the absolute depth. The resolution of the system is below 10 μm in both X- and Y-direction, and is therefore sufficiently accurate to detect typical surface defects such as scratches, dents, or deformations. To validate the measured values of the system, the results of an artificially generated 10.35 μm deep defect location were compared with those of a highly accurate mechanical stylus measurement.}, language = {en} }